Treatment of sickle cell disease is still largely symptomatic, though there continues to be considerable effort dedicated to the discovery of drugs to prevent or reverse HbS polymerization. Various techniques have been developed to facilitate the in-vitro evaluation of compounds for potential antisick1ing properties. However, none of these methods is easily amenable to large-scale screening of candidate compounds. We propose to develop a simple, robust method that will measure changes in intracellular viscosity caused by polymerization of HbS as well as antisickling agents. The technique is based on directing a beam of ultrasonic energy through a small sample of intact erythrocytes maintained under controlled oxygen tension and temperature. As HbS polymerizes at low pO2 and the intracellular viscosity increases, changes in the phase of ultrasound propagation, the amplitude, and the scattering cross section can be detected. By quantizing the degree to which an antisickling agent can reverse the effect, its effectiveness can be measured and compared. PROPOSED COMMERCIAL APPLICATIONS: Pharmaceutical and research laboratories engaged in the search for antisickling compounds have a strong need for a simple and automated means to screen candidate compounds. Use of the technique could be extended to monitor other structural blood changes, such as platelet function.